feat: add gnu inline asm syntax

[benjaminBrownlee]

Add the GNU inline assembly syntax. Let me know if you think the names of nodes or the tree structure should be different. The structure is a bit more lax than the specification, but I think it makes sense for simplicity.

closes #139

[amaanq]

I have something similar in my Objective-C grammar, is it more or less the same? https://github.com/amaanq/tree-sitter-objc/blob/7938eb5e135574095d8baf2c758e1f69d8cccafa/grammar.js#L372

I also have one for ms's version, __asm in the ms_asm_block

[benjaminBrownlee]

I think they are trying to do the same thing, but there are some issues with the objective-c version:

• input operands can be expressions; it is common to have casts in that context
• goto and inline are also qualifiers, and you can have multiple
• the clobber list should be a sequence of strings, not identifiers
• missing goto label list
• missing named registers

[amaanq]

I added the optional identifiers after the strings because of this
https://github.com/apple-oss-distributions/objc4/blob/c3f002513d195ef564f3c7e9496c2606360e144a/test/release-workaround.m#L26

Is this valid then only in Objective-C?

The other changes are good, I can then easily extend off of that from C which would be nice 🙂

[benjaminBrownlee]

We are talking about different parameters. The asm function has one required parameter (a string) and then up to four optional parameters separated by colons, which are the output operands, input operands, clobber list, and goto labels. Your link shows an example with an output operand but I was talking about the clobber list.

The last line of my test case uses a clobber list (with just "r2").

tree-sitter-c/test/corpus/expressions.txt

Lines 135 to 143 in a53e6a3

	asm volatile (
	"mov r0, %0\n"
	"mov r1, %[y]\n"
	"add r2, r0, r1\n"
	"mov %1, r2\n"
	: "r" (z)
	: "=r" (x),
	[y] "=r" ((uintptr_t) y)
	: "r2");

From what I can tell, the asm syntax for obj-c, c and c++ is the same, but may need to be updated to support other features (ie raw string literals).

[benjaminBrownlee]

For reference, the GNU specification for extended inline assmebly.

https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html

[amaanq]

We are talking about different parameters. The asm function has one required parameter (a string) and then up to four optional parameters separated by colons, which are the output operands, input operands, clobber list, and goto labels. Your link shows an example with an output operand but I was talking about the clobber list.

The last line of my test case uses a clobber list (with just "r2").

tree-sitter-c/test/corpus/expressions.txt

Lines 135 to 143 in a53e6a3

	asm volatile (
	"mov r0, %0\n"
	"mov r1, %[y]\n"
	"add r2, r0, r1\n"
	"mov %1, r2\n"
	: "r" (z)
	: "=r" (x),
	[y] "=r" ((uintptr_t) y)
	: "r2");

From what I can tell, the asm syntax for obj-c, c and c++ is the same, but may need to be updated to support other features (ie raw string literals).

Oh yeah, sorry about that! I appreciate the gnu reference - but I believe other compilers support it as well - can we rename the rules to drop the gnu prefix?

[benjaminBrownlee]

While the main compilers (clang, gcc) all support this syntax, it is a GNU extension and not a language standard. I guess I chose the gnu_ prefix to distinguish it from other assembly syntax which might be added, such as MSVC or ARMCC 4/5, which I would probably prefix with a msvc_ and armcc_ respectively.

You want to drop the prefix altogether and figure out the other syntax names later? Or perhaps there is a prefix you like better?

[amaanq]

If it's a gnu extension then no worries (I wasn't sure about that), this looks good!